Always start potatoes in cold water.
Dropping them into boiling water is a bad idea because the hot water will cook the outsides of the potatoes faster than the insides, leaving you with unevenly cooked taters. By the time they've fully cooked to the core, the outsides will be mushy and start to flake apart.
For most potato dishes it's important to add the potatoes to cold water and allow the water to come to a boil with the potatoes in the water. The potato starch can react as soon as it comes in contact with hot water, which will promote uneven cooking and mealy potatoes.
Keep Your Potatoes Hot
If you want a truly creamy taste and texture, you can't let the potatoes cool before mashing—you want to start getting busy with them as soon as possible after they've been boiled and drained.
Soaking potatoes in water helps remove excess starch. Excess starch can inhibit the potatoes from cooking evenly as well as creating a gummy or sticky texture on the outside of your potatoes. Cold water is used because hot water would react with the starch activating it, making it harder to separate from the potatoes.
Boiling water takes forever, so you decide to speed things up by filling the pot with scalding hot tap water instead of cold. DON'T DO IT! Why? Well, because your hot water from the tap can contain contaminants.
Give them a cold water bath: Once your potatoes are chopped, toss them into a large bowl. Then cover the potatoes completely with cold water and let them soak for at least 30 minutes (or up to overnight). This will help to rinse off the excess starch and help the potatoes crisp up beautifully in the oven.
The Mistake: Overworking the Potatoes with a Food Processor, Blender or Mixer. Too much — or too vigorous — mashing will produce gluey potatoes. Your best tool is an old-fashioned masher, fork, ricer or food mill.
Prepping the potatoes ahead of time
To save time on peeling and chopping on Thanksgiving Day (or any other day that includes mashed potatoes), you can peel the spuds and keep them submerged in a bowl of water in the fridge, whole or cut up, for hours — even overnight — before boiling.
I have done it both ways, depending on whether I'm in a hurry. Ideally, you will fill the pot with your spuds and then add cold water to that pot and then add to heat.
As with pasta water, there's a reason to liberally salt the water in which the potatoes will cook: As the starches in potatoes warm up, they open up and absorb water (and salt if you season the water). When they're finished cooking, the cells close off.
Boil 10 to 12 minutes for cubed, 15 to 20 for whole medium-sized, or 25 to 30 for whole russets. Check with a fork or knife. Potatoes are done when they are tender enough that a utensil easily slides into the middle.
“Salting the water not only seasons the potato, but it also allows it to boil to a hotter temperature. This in turn cooks the potatoes' starch more thoroughly, resulting in a more creamy texture [for mashed potatoes],” says Sieger Bayer, Chef and Partner at The Heritage.
Boiling your potatoes for a little bit before roasting helps make sure that you get that beautiful crisp crust on the outside. If you don't parboil your spuds, the outside skin will remain quite tough, meaning that whatever fat you use will not be able to get inside the cracks.
Potatoes are not hardy plants, so in general they are planted in spring from mid March to late April and can be harvested anywhere between June and October. In milder regions potatoes may be planted earlier than in colder regions.
Restaurants prepare the potatoes ahead by boiling and mashing just the potato, then just before serving, it is mixed into boiling cream (or milk or even broth or a combination thereof) to reheat it and make it nice and creamy.
Do NOT add cold liquid. Make sure the milk or cream you add to your potatoes is HOT. This helps it absorb better so you don't feel the need to overmix. Overmixing is bad.
Milk: Milk adds to the richness of the potatoes. Use at least 2% milk, but preferably whole milk. Chicken broth: This adds a richer flavor than if you would just use water. Butter: Butter is always a good idea.
Here's how to do it: For every pound of potatoes in your mash, drizzle 1 tablespoon of melted butter over the dish and fold it gently into the potatoes. If the mash is still too gluey for your liking, repeat the process with another tablespoon of butter.
The most important part here is that you use cold water instead of boiled – if you boil the water first, the outside will cook faster than the inside resulting in an uneven texture. Cubed spuds will take around 15 minutes where larger chunks or whole new potatoes will be 20-25 minutes.
Season with salt and pepper. Plan on 1/3 to 1/2 pound potatoes per person for your feast.
The most ubiquitous variety, russets, will mash smoothly and readily absorb whatever delicious additions you incorporate, whether you go with the classic butter and cream combination or mix things up with sour cream or even roasted garlic and olive oil.